Conductivity modification of ZnO film by low energy Fe ion implantation

In this paper we report the structural, optical and electrical behaviours of ZnO films implanted with 300 keV Fe¹⁰⁺ ions. From UV-vis spectroscopy it is observed that the band gap of the films decreases after implantation. Photoluminescence yield seems to increase in the implanted samples. From Hall measurements it is observed that the unimplanted sample shows n-type conductivity for the entire temperature range (100-300 K), whereas after implantation the samples show p-type conductivity for ≤200 K. The DC resistivity of the implanted samples is found to be lower than that of the unimplanted sample. We have found that the magnetoresistance of our samples is positive in the temperature range 200-300 K, but it becomes negative below 200 K.     

Optimal placement of stereo sensors

Autonomous wireless devices such as sensor nodes and stereo cameras, due to their low cost of operation coupled with the potential for remote deployment, have found a plethora of applications ranging from monitoring air, soil and water to seismic detection and military surveillance. Typically, such a network spans a region of interest with the individual nodes cooperating to detect events and disseminate information. Given a deployment of sensors and targets over a region, a sensor pairing is desired for each target that optimizes the coverage under certain constraints. This problem can be modeled as an integer programming problem and solved using branch-and-cut. For larger problems, it is necessary to limit the number of variables, and a GRASP routine was developed for this purpose. Valid cutting planes are developed and computational results presented. Research supported in part by NSF grant numbers DMS–0317323 and CMS–0301661.     

Anti-arthritic activity of Tin oxide-Chitosan-Polyethylene glycol carvacrol nanoparticles against Freund’s adjuvant induced arthritic rat model via the inhibition of cyclooxygenase‑2 and prostaglandin E2

Rheumatoid arthritis (RA) results in increased rate of mortality in millions of people worldwide. Research utilizing Tin oxide – Chitosan- Polyethylene glycol Carvacrol (SCP-CAR) nanocomposites has gained increased attention because of its multipotent properties and application in diverse fields including medicinal preparations. The aim of the investigation was to synthesize and to examine the anti-arthritic ability of SCP-CAR nanocomposites against CFA -induced RA in rats. Arthritis induction was done by injecting 0.1 ml of Complete Freund’s adjuvant (CFA) intradermally. Body weight, weight of organs, hind paw volumes and arthritis score was assessed and the levels of inflammatory modulators such as IL-6, IL-1β, IL-10, TNF-α, PGE2 and COX-2 was examined using assay kits. Lipid peroxidation status, antioxidant enzyme activities and levels of liver function enzymes were evaluated using standard procedures. Histopathological changes observed in hind limb of experimental animals were viewed under microscope using H& E staining. The SCP-CAR nanocomposites treated arthritic animals showed increased bodyweight and reduced hind paw volume, organ weight and arthritis score together with elevated antioxidants status and depleted proinflammatory cytokines. Histopathological observation also showed reduction in bone destruction and penetration of inflammatory cells following treatment with SCP-CAR nanocomposites. Thus, together the findings depict the anti-arthritic and anti-inflammatory potential of SCP-CAR nanocomposites suggesting that it could be used as potent therapeutic agent to treat animals against arthritis induced by CFA.     

Composition-dependent crystallization behavior of copolyperoxides from methyl methacrylate and 4-vinylbenzyl stearate

To study the composition-dependent crystallization behavior of copolyperoxides, herein a series of copolymers were prepared by varying the ratios of methyl methacrylate (MMA) and 4-vinylbenzyl stearate (VBS) under 100 psi oxygen pressure using AIBN as an initiator at 50°C in toluene. Both ¹³C NMR and electron impact mass spectroscopy (EI-MS) approved an alternative placement of either of the monomer and peroxy (–O–O–) links throughout the polymer chain. Thermal stability of the resulting copolyperoxides was investigated by thermogravimetric analysis (TGA) and the degradation fragments have been recognized from EI-MS study. In addition, differential scanning calorimetry (DSC) displayed an endothermic peak as well as an exotherm associated with the melting of the side chain crystalline domains and degradation of –O–O– links in the polymer main chain, respectively. Furthermore, DSC thermograms unveiled a systematic decrease of the crystalline melting temperature (T_m) with the enhancement of MMA content in the copolymers. Small angle X-ray scattering (SAXS) revealed the existence of lamellar morphology (depends on VBS content in the copolyperoxide) in the synthesized polyperoxide materials, further supported by atomic force microscopy (AFM) analysis showing a layered fibrillar assembly with multiple heights of the lamella. The significant crystalline nature of the polyperoxides was further evidenced from the appearance of lattice fringes in the transmission electron microscope (TEM) micrographs. The crystalline morphology with birefringent texture was further evidenced from the polarized optical microscopy (POM) study. Thus, the present study reported the effective variation of crystalline behavior in copolyperoxide materials with the incorporation of MMA units in the copolyperoxide chains.     

Unsymmetrical trimesogens exhibiting the undulated twist grain boundary (UTGBC*) mesophase

A new set of trimesogens consisting of a cholesteryl ester, a biphenyl and an azobenzene mesogenic segment joined together through either odd-even, even-even or odd-odd central alkylene spacers has been synthesized and the liquid crystalline properties investigated. The trimesogens having even-even and odd-odd central alkylene spacers exhibit the undulated twist grain boundary phase (UTGBC*) mesophase over a temperature range of ~40-50°C.     

Cu–N‐heterocyclic carbene‐catalysed synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from one‐pot tandem coupling of o‐phenylenediamines and terminal alkynes

A series of new benzimidazolium chlorides bearing N,N′‐benzyl, 2,4,6‐trimethylbenzyl and 2,4,6‐triisopropylbenzyl substituents have been designed and synthesized from various o‐phenylenediamines. Subsequently, corresponding Cu‐based N‐heterocyclic carbenes (NHCs) were generated in situ in the reaction medium which represents a new application of NHCs exploiting distinct catalytic property towards intermolecular cyclization reaction cascade for the synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from o‐phenylenediamines and terminal alkynes. The outcome of the cyclization reaction product depends upon the N,N′‐substituents present on the benzimidazolium chlorides.     

Camphor-10-sulfonamide-based prolinamide organocatalyst for the direct intermolecular aldol reaction between ketones and aromatic aldehydes

Prolinamides derived from l-proline and N,N-dialkyl 2-aminocamphor-10-sufonamides have been synthesized and used as organocatalysts in the direct intermolecular aldol reaction. Reactions of several aromatic aldehydes with cyclohexanone, cyclopentanone, 4-oxa and 4-sulfa-cyclohexanones and acetone are investigated employing 1a as an organocatalyst. Very high to excellent selectivities are obtained in these direct aldol reactions.     

Physikalisch-chemische Vorgänge beim Wachsen von Herpes tonsurans

Ohne Zusammenfassung Deutsch von Alfred Kuhn (Leipzig).